Zilver PTX: Two-Year Results Confirm Benefit of Paclitaxel-Eluting Stent in PAD

January 18, 2011

January 18, 2011 (Miami Beach, Florida) — Follow-up data from the Zilver PTX (Cook Medical, Bloomington, IN) study of peripheral endovascular therapy for the treatment of femoropopliteal disease confirms the positive results observed at 12 months, with investigators showing the self-expanding, paclitaxel-eluting stent to be superior to both percutaneous transluminal angioplasty and bare-metal stenting [1].

Presenting the results this week at the International Summit of Endovascular Therapy (ISET) 2011 in Miami Beach, FL, Dr Michael Dake (Stanford University, Palo Alto, CA) said there was a 50% relative reduction in the risk of restenosis at two years, a large success given the difficulties in treating these lesions with other therapies.

Speaking during the late-breaking clinical-trials session, Dake said the primary end point of the Zilver PTX study, primary patency at 12 months, was maintained at two years. This improved patency translated into improvements in clinical outcomes, such as improvements in walking speed and walking distance and a preservation of the Rutherford score, a designation used to evaluate the severity of peripheral artery disease (PAD).

One Year Results Confirmed

Briefly, the ZILVER PTX trial had two randomization protocols. In the first, patients were randomized to treatment with the Zilver PTX stent, a polymer-free, paclitaxel-eluting peripheral stent, or to traditional percutaneous transluminal angioplasty. There was a second randomization, known as the provisional stenting group, among patients who failed the traditional angioplasty, with failure defined as >30% residual stenosis or a >5-mm-Hg pressure gradient following two to three minutes of angioplasty balloon inflation. Patients who received a suboptimal angioplasty were then randomized to a bare-metal Zilver or Zilver PTX stent.

In September, Dake reported the 12-month results of the Zilver PTX trial, covered by heartwire , at TCT 2010. At one year, 83.1% of the stented segments treated with the Zilver PTX were still patent, compared with only 32.8% of the vessels in the angioplasty-treated patients (p<0.01). The Zilver PTX stent also bested the Zilver bare-metal stent.

At two years, event-free survival--defined as freedom from death, amputation, TLR, or worsening Rutherford score--was significantly better with the Zilver PTX stent when compared with patients who underwent traditional angioplasty (86.6% vs 77.6%, p<0.01). Among a subset of 56 patients who underwent successful angioplasty and were followed long term (>12 months), 57.8% had patent vessels at two years, whereas 74.8% of the 187 lesions treated with the Zilver PTX stent were patent.

In the patients who underwent provisional stenting after failed percutaneous transluminal angioplasty, the curves began to diverge after one year, with 62.7% of 56 lesions treated with the bare-metal Zilver stent patent at two years compared with 81.2% of the 56 lesions treated with the Zilver PTX stent. 

"This represents, effectively, a 50% reduction in restenosis at 24 months in favor of Zilver PTX over the Zilver bare-metal stent," said Dake.

Speaking with heartwire , Dr Ramon Quesada (Baptist Cardiac and Vascular Institute, Miami, FL), who was not affiliated with the Zilver PTX trial, said that PAD is a common clinical problem and that very few treatments in the past have been effective.  For example, he said, there was no difference in outcomes among femoropopliteal-disease patients treated with a sirolimus-eluting, polymer-coated stent and those treated with a bare-metal stent in the SIROCCO II trial.

In addition, there are high rates of restenosis with femoropopliteal disease, noted Quesada, likely because of the location of diseased vessels, suggesting mechanical factors and/or stress might have an impact on the long-term effectiveness of the stent. The lack of late catch-up observed at two years is reassuring, he told heartwire . During the presentation, Dake noted that stent fracture occurred in just 0.9% of 546 Zilver stents implanted, a low rate, and that the next X-ray evaluation will occur at three and five years.

Dake consults and/or serves on the advisory board of Cytograft Tissue Engineering, CVRx, Endoluminal Sciences, NovoStent, Summit Life Sciences, TriVascular, Vatrix, and WL Gore and has received research grants from Abbott Vascular and Cook Medical. Quesada reports honoraria, consulting, and/or serving on the advisory board of Abbott, Boston Scientific, Cordis, NMT, and St Jude Medical.